The present invention broadly relates to methods and apparatus for moving railroad cars. More particularly, my invention relates to cables or straps capable of temporarily substituting for defective draw bars during railroad car maneuvering. The invention pertains to art classified in U.S. Class 213, subclass 67R and Class 224, subclass 58.
Modern railroad cars are coupled together by complex draw bar systems. When these draw bars fail, a section of the train or an individual car must be serviced. Stranded or disabled cars are often moved out of the way of traffic onto a siding. They must be moved out of the way of traffic as soon as possible for safety and efficiency. Temporary maneuvering of railroad cars is conventionally effectuated by heavy tow chains.
Chains can be cumbersome and difficult to work with, particularly in cold, dark and rainy conditions. While chains have very high tensile strengths they are relatively brittle, making them somewhat unreliable when exposed to the violent forces caused by the take-up of slack as a train begins to move. In other words, when a disabled car is hooked to the operative portion of a train by chains, as the slack between the cars is taken up, the force of the locomotive is amplified as it travels through the cars to the chains holding the disabled car. Therefore, a sudden jerk is exerted on the chains increasing the likelihood of their immediate or subsequent failure.
When chains break, flying metal can injure bystanders. The dangerous whipping effects of a snapped tow chain are well known. Replacement of the chains by steel cables is inappropriate for the same reasons. When steel cables fail, the whipping motion is even more severe. Even where the temporary hook-up proceeds smoothly, chains take significant time to install and then remove. Because of the tremendous pull forces involved, metal parts can bind and become stuck, complicating the removal process. A more reliable, and easier-to-use replacement for the conventional heavy metal tow chain is thus desirable.
These disadvantages, coupled with the great weight of high strength chains and the difficulty in managing high strength cables as well as the time required to deploy such cables, begs for a more appropriate, safer, lighter-weight, easily deployed system to move disabled railroad cars.
Webbing straps are well know to the art of towing and/or load binding. Webbing straps have long been employed for the towing of automobiles, trucks, and particularly off-road vehicles. Furthermore, webbing straps have been used to secure loads in the trucking industry, airline industry, and by individuals, for quite some time. Reese, U.S. Pat. No. 3,955,734 discloses a tow strap assembly which is adjustable and has adjustable eyes on either end. The nature of the adjustments for this strap allows the strap to be looped back around itself several times and employs mechanical clamps and other keeper systems to dispose the strap at a user selected length. The military air services have employed webbing straps not only to strap down and hold loads, but also to pick-up loads from the ground in order to hoist them into fixed as well as rotary wing aircraft.
However, the use of webbing straps in the railroad industry is somewhat limited. Hanula, U.S. Pat. No. 4,635,804 discloses the use of a yoke to couple railroad cars using two straps. This yoke calls for the metallic portion of the yoke itself and a bridge to bear the loads where the strap contacts elements of the railroad cars.
As mentioned above it is therefore desirable to develop a strap of relatively light-weight yet high tensile strength that can be employed to temporarily couple a disabled railroad car to the operative portion of a train. If failure were to occur, such a strap would not suddenly snap, but rather it would more-slowly tear apart. When it does break the light-weight nature of the strap prevents it from developing the momentum present in a chain or cable which has suddenly failed. Another significant advantage of a strap system would be that it would be relatively adjustable. Furthermore, a strap system would afford a more flexible connection than chains. In other words, the strap would give rather than fail when subjected to a sever sudden shock. Such shocks are common when trains first start up as the locomotive pulls the slack from each coupling. This shock has an a cumulative effect as it passes down the train from the locomotive. Therefore, if the temporarily coupled disabled cars were near the end of the train the shock forces would be too great for the relatively brittle chain to endure. Conversely, the strap assembly would stand a better chance of giving and holding when the shock was encountered.
Even though fabric straps have advantages over tow chains, no prior fabric strap of which I am aware has ever worked reliably in the railroad environment. The strap must be carefully constructed to work at all. Notwithstanding the strap's construction, it must be carefully and precisely bound about the disabled draw bar sections to avoid snapping.